1. Field of the Invention
The present invention relates to a manufacturing method of a solar cell module, and to a solar cell and a solar cell module. In particular, the present invention is suitable to be applied to a solar cell module containing double-side light receiving solar cells in which sunlight may incident from front and rear faces of them, and a manufacturing method thereof and a solar cell to be applied to such solar cell module. The present invention is suitably applicable also to the solar cell module which contains not double-side light receiving solar cells but one-side light receiving solar cells.
2. Description of the Related Art
In recent years, against the backdrop of problems such as depletion of petroleum resources and global warming, development and spread of clean energy source without using petroleum resources have been taken up as a global-scale challenge. Photovoltaic solar systems, which use infinite solar energy without emitting CO2 and such, have been gaining attentions with an expectation as playing a major role towards the solution for such a challenge.
A typical photovoltaic solar system employs a solar cell module generally constituted from several tens of solar cells arranged in a planar state, in order to protect the solar cells as a power production source from being injured and to facilitate handling of the solar cells. Here, the solar cell module is commonly configured as a rectangle, about 1 m to 2 m on a side, so that the solar cells may be arranged efficiently within a given area, and the handling in transport and installation may be facilitated.
On the other hand, as shown in (a-2) of FIG. 28, a shape of an ingot (single crystal silicon) 30, which is used as a substrate material for the solar cells, is cylindrical by the nature of a manufacturing method thereof. Accordingly, slicing the ingot as it is to produce a cell substrate 31 necessarily makes a shape of the solar cells circular. This results in a problem that a filling rate of solar cells 10 to the solar cell module 20 becomes low due to a large area of spaces between the solar cells, even when the solar cells are arranged in a manner most efficiently as shown in (a-1) of FIG. 28, for example.
By contrast, as shown in (b-1) and (b-2) of FIG. 28, the filling rate of the solar cells 10 may be improved by making the shape of the solar cells 10 square. However, at the same time, this causes a problem that an unused area in the ingot 30 (hatched area in (b-2) of FIG. 28) that is not used as the substrate 31 becomes large, thus considerably decreasing use efficiency of the ingot.
Further, as shown in (c-1) and (c-2) of FIG. 28, making the shape of the solar cells 10 regular hexagonal may improve the filling rate of the solar cells 10 as compared to the case of the circular shape, and may also improve the use efficiency of the ingot 30 as compared to the case of the square shape. However, in this case, the solar cell module 20 still includes spaces at which the solar cells 10 may not be arranged, and the unused area of the ingot 30 that may not be used as the substrate 31 remains to no small extent.
In order to address such a problem, Japanese Patent Application Laid-Open No. 2001-94127 describes a solar cell module, which may improve both the filling rate of the solar cell 10 and the use efficiency of the ingot 30. According to this prior art invention, as shown in FIG. 29B, the substrate 31 is cut out of the ingot 30 as a regular hexagon that is larger than a regular hexagon inscribed in an outer circumference of the ingot 30 and smaller than a regular hexagon in which an outer circumference of the ingot 30 is inscribed (the shape cut out in this manner is hereinafter referred to as “pseudohexagon”). With such an arrangement, it is possible to suppress the unused area of the ingot 30 that is not used as the substrate 31, and the use efficiency of the ingot 30 may be improved.
Further, in this prior art invention, when producing the solar cell 10 from the substrate 31 that has been cut out in the above manner, the solar cell 10 is divided into two or four pieces by a line P-P′ and/or a line Q-Q′ shown in FIG. 29B, and these pieces are arranged as shown in FIGS. 29A or 29C. With this, the area of the spaces at which the solar cells 10 may not be arranged may be suppressed, thereby improving the filling rate of the solar cell 10.
In addition, Japanese Patent Application Laid-Open No. H09-148601 discloses an arrangement in which a solar cell in a regular hexagonal or pseudohexagonal shape is divided into two pieces by a straight line connecting two opposing apexes or a straight line connecting center points on two opposing sides, and these pieces are arranged in the solar cell module. FIG. 30A illustrates such an arrangement of the solar cell module according to this prior art invention, and FIG. 30B shows a cross-section taken at a line R-R′ of FIG. 30A.
It is additionally mentioned that, according to this prior art invention, the solar cells 10 are arranged in the solar cell module 20 so that polarities of the respective cells face the same direction. The solar cells 10 are electrically connected so that one of both surfaces of one solar cell 10 is connected to the other of the both surfaces of a solar cell 10 adjacent thereto are connected with an inter connecter 21.
Further, Japanese Patent Application Laid-Open No. H11-354822 and Japanese Patent Application Laid-Open No. 2002-26361 describe an arrangement in which the solar cells are arranged in a solar cell module so that the directions that polarities of one solar cell face is opposite to the directions that polarities of a solar cell adjacent thereto face. FIG. 31A illustrates such an arrangement of this prior art invention, and FIG. 31B shows a cross-section taken at a line S-S′ of FIG. 31A. According to this prior art invention, the surfaces on the same side of the respective solar cells 10 that are adjacent to each other are connected with the inter connecter 21. In this case, it is unnecessary to lead the inter connecter 21 around the cells from one side to the other, and therefore making an electrical connection may be facilitated. Moreover, it is possible to fill the space between the adjacent solar cells 10, and thus improving filling rate of the solar cells 10 to that extent.
In producing a solar cell module, a cumbersome work is required in order to arrange the solar cells and to connect electrically between the cells that have been arranged. In particular, when the solar cell is divided into four small pieces as shown in FIG. 29C, the arrangement becomes even more cumbersome compared to the arrangement of solar cells as they are without dividing. While the above-described Japanese Patent Application Laid-Open No. 2001-94127 shows the state after the arrangement of the cells is completed, any step taken during the arrangement or electrical connection is not described at all.
According to the case shown in FIG. 29C, four types of the solar cells are provided as the solar cells to be arranged. In this case, a problem arises that determination as to which type of the cell should be arranged at a certain position becomes difficult when arranging the four types of the solar cells in the solar cell module. It becomes particularly difficult to instantly determine the type of a solar cell to be selected for a certain position in terms of arrangement directions of electrodes on a solar cell, in a case in which the solar cells are to be arranged so that the polarities of the surfaces of the two adjacent solar cells are inversed as illustrated in FIGS. 31A to 31B.